The invention relates to artificial heart valves, that is, to a prosthesis for the replacement of aortic and mitral valves of a heart, comprising an annular body receiving a plurality of pivotal flap elements which annular body can be mounted into the aorta or the mitral valve ring and can be retained therein by surgical procedures so that the flap elements open or close the passage through the valve ring depending on their pivot positions.
A prosthesis, that is an artificial heart valve, of this type is known from WO-A-8504094. For some decades now, heart valve prostheses have been implanted into the aorta leading away from the heart. The first artificial heart valves were ball-type check valves which, with time, were replaced by more sophisticated designs. Heart valves with single flap elements and also with three-flap elements are known. The valve disclosed in WO-A-85 04094, for example, is a three-flap valve. Heart valves with flap elements use an annular support body on which the flap elements are pivotally supported and which is inserted for example into the aorta and is secured in position by a surgical procedure such as suturing.
The annular body is generally provided with shaft-like projections, which extend into corresponding openings of the flap element thereby forming a pivot joint. The flap element generally is provided with such openings at opposite sides with a shaft extending from the annular body into each of the opposite openings. However, also other solutions are known from the state of the art, wherein shaft-like projections extend from the flap elements into corresponding openings formed in the annular support body.
The opening and closing of the flap element, or of the flap elements, if more than one flap element are provided in the annular body, occurs in principle over long periods of use in a trouble-free manner since certain components of the blood act as lubricants which reduce friction in the joint parts.
However, all artificial heart valves of this type have the disadvantage that the joint area between the annular body and the flap elements negatively affect the flow dynamics of the blood through the opening of the annular body so that zones are formed in the joint areas in which blood is stagnant. This effect is generated also by the fact that the flap elements never move fully away from the annular body during the heart pumping cycle. In the areas in which the blood is stagnant in these valves blood clots are formed which are released from time to time and are then transported with the blood flowing through the aorta into remote body parts for example into the brain where they may block the blood passages with catastrophic results for the person affected thereby.
It has been tried with sophisticated designs to reduce to a minimum the areas near the joints where the blood can stagnate in order to minimize the chances of blood clot formation and it has also been tried to arrange the joints or the joint areas in such a way that the areas between the joint and the annular body are flushed by the blood flowing through the annular body so that these areas are kept “clean”, in order to avoid the formation of blood clots but no really satisfactory solutions have been found. Consequently, heart valves with two flap elements (so-called double wing flaps) or ball-type heart valves which have no joints but which have substantial other disadvantages are still being used.
It is therefore the object of the present invention to provide a heart valve of the type described above which however does not have the disadvantages of the state of the art heart valves as pointed out above. The heart valve should, in its design, be adapted with regard to its physical-mechanical operation to the design of the natural heart valve and be capable of remaining in the body indefinitely after implantation while providing for trouble-free operation without the danger of forming blood clots. Also, the decreasing and increasing pressure of the blood as it occurs during opening and closing of the valve should correspond essentially to the pressure gradients occurring naturally in the heart during the opening and closing of the natural heart valves. It is further an essential object of the invention to provide an artificial heart valve of the type described above, which, after implantation, does not require the continuous administration of medication in order to prevent the formation of blood clots so that, in principle, the patient can live after heart valve implantation normally, that is, without having to take medications.